Design Considerations for Ceramic Matrix Composite High Pressure Turbine Blades

Abstract

Issues associated with using SiC/SiC Ceramic Matrix Composite (CMC) materials for High Pressure Turbine (HPT) rotor blades are explored. SiC/SiC materials have higher temperature capability than current HPT superalloys. The strength versus temperature characteristics of SiC/SiC CMCs differs from that of superalloys. Stress analyses were done for a NASA specified notional single aisle aircraft engine blade to be available in the N+3 time frame, (beyond 2030). Stacking, the relative position of hub and tip sections, depends on both pressure and centrifugal forces, and material density. The effect of blade stacking on blade stresses is examined. The change in stresses as the rotation rate varies is examined. The change in engine weight, and thus fuel consumption, due to changes in engine size as the rpm changes is discussed. SiC/SiC CMC materials are generally not isotropic. The effect on stresses and strains of a directional variation in Young’s modulus is examined. Shrouding metallic HPT rotor blades is not common. Shrouding SiC/SiC CMC rotor blades may be feasible due to the lower density, and thus lower centrifugal loads, of SiC/SiC blades. The increase in stresses due to shrouding a SiC/SiC blade is discussed.

Stress Analysis and Life Prediction of a Ceramic Matrix Composite Vane Using a Micromechanics-Based Approach

“…The high temperature capability combined with their low density as compared to titanium and nickel-based alloys make ceramics and their composite derivatives ideal candidate materials for the hot sections of turbine engines tailored for these requirements [1]. The use of these materials allows for the potential operation of gas turbines at higher inlet temperatures without the need for external cooling, which in turn reduces the overall weight while increasing efficiency and reducing the noise level during engine operation while maintaining low Nitrogen Oxide (NOx) and Carbon Monoxide (CO) emissions [2,3]. Furthermore, as compared to monolithic ceramics the reinforcements in ceramic matrix composites (CMCs) give them superior toughness and durability even at elevated temperatures [4].…”